Nakayama Tetsugaku - Braid Slave ch.2

A school nurse who harasses little boys coming for treatment gets the table turned on her by the protagonist (yes, he is the good guy here), who manage to swipe the soaked cloth and drug her. It turned out the boys she tormented asked him to punish her.
The scene is excellent in all terms, but I had to cut the 4th page for content issues.
Source: g.e-hentai.org